1. Technical Field
The present invention relates to the technical field of sputtering devices, and particularly to a multiple cathode sputtering device.
2. Related Art
A sputtering device is widely used in the field of semiconductor devices and liquid crystal display devices to form metallic thin films and insulation films.
Reference numeral 102 in FIG. 10(a) shows an example of a sputtering device.
This sputtering device 102 has a vacuum chamber 111, with a substrate holder 113 arranged on the bottom of the vacuum chamber 111, and a target holder 115 arranged close to the ceiling of the vacuum chamber 111 at a position above the substrate holder 113. A plurality of cylindrical shield tubes 106 are provided on a substrate holder 113 side surface of the target holder 115 (in this drawing three shield tubes 106.sub.1 -106.sub.3 are shown).
Targets 105.sub.1 -105.sub.3 are arranged one each inside the shield tubes 106.sub.1 -106.sub.3, and when a substrate on which a film is to be formed is placed on the substrate holder 113 the substrate and each of the targets 115 face each other.
When sputtering is carried out with this sputtering device 102, among particles ejected from the each of the targets 105.sub.1 -105.sub.3, those that are ejected diagonally become deposited to the shield tube 106, and only particles that fly out vertically can pass through the shield tube 106.
Reference numeral 112 in FIG. 10(b) represents as substrate mounted on the substrate holder 113, and if sputtering particles that have passed through the shield tube 106 are incident on the substrate 112, an angle formed by those sputtering particles and the surface of the substrate 112 becomes a minimum of .phi.(incident angle is .pi./2-.phi.). When the particles are incident at this angle .phi., the incident angle of the sputtering particles becomes maximum.
A rotating shaft 117 is attached to a rear surface of the target holder 115. The rotating shaft 117 is airtightly lead through to the outside of the vacuum chamber 111. Rotation of the rotating shaft 117 causes rotation of the target holder 115, and each of the targets 105.sub.1 -105.sub.3 can be horizontally rotated parallel to the substrate holder 113. Reference numeral 118 represents the rotational axis of the rotating shaft 117.
With this type of sputtering device 102, if sputtering is carried out while rotating the target holder 115, a thin film is uniformly formed on the surface of the substrate 112 with a small incident angle of the sputtering particles to the surface of the substrate 112. Accordingly, uniform film formation is also possible inside microscopic holes having a high aspect ratio.
However, since sputtering particles deposit to the inner walls of the shield tubes 106.sub.1 -106.sub.3, a thin film is also formed at this section, and a problem occurs in that this film breaks up into smallness dust. Also, even if surface treatment to prevent smallness dust being generated is performed on the inner wall surfaces of the shield tubes 106.sub.1 -106.sub.3, it is difficult to insert a spray gun inside the tube.
Also, when reactive sputtering is carried out, not only sputtering gas but also reactant gas infiltrates into the shield tubes 106.sub.1 -106.sub.3, which causes problems such as a metallic target surface being nitrided (for example, TiN being formed on a Ti target surface), a reduction in sputter yield, and lowering of film deposition rate.